The invention relates to a directive broadband antenna element of V-shaped dipole type having bent wire or strip-shaped conductors forming dipole elements, a feed point being situated at the apex of the V and the radiation direction substantially coinciding with the line of symmetry through the apex of the V.
In particular it relates to a directive antenna element which can be used for example, as a broadband primary radiator for illuminating a parabolic reflector or an electromagnetic lens. It is desirable to place the primary radiator such that its center of radiation coincides with or is near to the focal point in the illuminated reflector or lens. This should be true across the whole frequency range of the primary radiator.
If the primary radiator is to be used in multilobe antennas, special requirements must be met, regardless of whether it is of the reflector or the lens type.
In a reflector antenna the reflected wave will pass the primary radiator, while for example in a circular lens antenna of Luneberg type with 360.degree. bearing angle the primary radiator is passed by the waves transmitted from the opposite radiators.
The primary radiator disturbs the passing waves because its aperture has a blocking effect and because its mechanical structure has a certain shadowing effect. The blocking can be avoided by arranging the antenna element such that the polarization of the passing wave is orthogonal relative to that of the primary radiator. The shadowing effect can be reduced by making the structure of the primary radiator plane shaped and as small as possible. With such a shape for a directive antenna elements, it is difficult to obtain a large broadband performance and a good directive effect.